One of the most intriguing developments in modern tennis is using principles of martial arts. The best performers do not meet the ball head-on; they deflect it. Top players apply force to turn the ball around and send it back across the net. The ball enters the racquet and slides across the strings before coming off the racquet. On groundstrokes, especially on topspin strokes, players direct the force up and across the body, rather than straight toward the intended target, turning the incoming power of the ball in an almost effortless manner.

As you practice this, you may be surprised at how different your wrist effort is, putting much less strain on it and your arm. A player drives toward a ball and, when almost in contact with it, breaks the plane and accelerates forcefully in a different direction. From physics, we know that force equals mass times acceleration, not just mass times plain velocity. A top player may be exerting force forward and up, but, at contact, breaks that plane and accelerates the racquet even more forcefully across the body.

On the forehand, for example, top pros, contract the biceps and pectorals sharply while lifting the right side of the trunk and leaning the whole torso to the left (for a right-hander). It's as if you're exerting the force needed to pull something heavy up and toward you—rather than extending the arm outward. Keep your eye on the player, rather than the ball, and see him or her closing in the arm towards the left side of the body as if hugging it.

This is a huge departure from conventional tennis coaching, and kids do it naturally. They should not be coached any other way, lessening their potential to be great.

The best topspin one-handed backhands on the tour, such as Fededrer’s, Henin’s, and Kuerten’s are hit up and, on contact, across the ball to the right. The best sliced backhands on the tour are also hit across, as are serves, including the best of all time. This across-the-body motion applies to the best strokes, even volleys.

Old champions like Bill Tilden, Jack Kramer, Rod Laver, Bjorn Borg, Chris Evert on her backhand, Billy Jean King, Monica Seles and Steffi Graf did not meet the ball head on. They deflected it back. You can add to this list most of the better players from the 1990s on.

How should you apply this martial arts idea to your game? Simple and easy. Wrap the racquet across your body. When hitting the forehand, bend your arm, bringing your fist toward the opposite shoulder. Rather than hitting "five balls in a row," as taught in conventional tennis, imagine hitting the first one and avoiding the other four. Change your path across the body, not forward. The power in the contraction of your biceps and pectorals will make the ball explode off your racquet. Notice how natural it becomes to produce topspin, as the easiest path is also an upward move.

Notice how top pros hit use the racquet face angle to deflect and direct the ball, while the arm moves on its own path. This is how smaller players handle the onslaught of a bigger or stronger player and send the ball back even faster than it came onto his or her racquet. Martial arts proves that deflection is the best way to combat a superior force.